1. Field of Application
This invention relates to articulable joints; and more particularly to joints articulable about only a single axis of rotation.
2. Description of the Prior Art
Articulable joints are utilized whenever two members are to be connected together so that the members can move with respect to each other. Some such joints are quite versatile permitting movement of the members with respect to each other, about plural axis of rotation; a first such axis of rotation, for example, passing through such members in a longitudinal direction; and a second such axis of rotation, for example, passing through such members in a transverse direction. However, the more versatile the joint, the more complex and costly it usually is. Complexitiy and cost of such articulable joints may increase even more if the joint is to permit a person to selectively move the members with respect to each other, while at the same time maintaining the members in position once so moved; especially if one or both of the members is relatively heavy, and/or if one of such members creates a relatively large moment about its axis of rotation.
Not all members which are to be joined together, so that the members can move with respect to each other, require a joint permitting rotation about multiple axes of rotation. If such members are to be joined so that movement about only one axis is sufficient the versatility, complexity and cost of multiple axes joints is most probably not warranted. A joint which facilitates selective movement about a single axis, and which retains the members in position when so moved, without the need for tools or a release and locking means, may still be required for particular applications. One such application is found in lamp and lighting fixtures.
Many lamps and lighting fixtures connect the lamp socket, into which the light bulb is screwed, to its carring member (an arm or pole) by way of a joint that permits movement of the lamp socket about an axis of rotation perpendicular to an axis passing through the lamp socket carrying member. Quite often the lamp socket is disposed in a bullet or globe like housing which is, in turn, connected to a carrying member by such a joint. Selective positioning of the housing, or bulb socket, of such units may require release of a locking device before being able to move the lamp unit, and subsequent tightening of the locking device after such movement if the lamp is to maintain its position. Quite often the locking device comprises friction type fittings which deteriorate with age and continued movement of the carrying unit, and releasing and tightening of the locking device.